Subwavelength localization of near fields in coupled metallic spheres for single-emitter polarization analysis

We numerically demonstrate selective near-field localization determined by the polarization state of a single emitter coupled to a plasmonic nanocluster. Seven gold nanospheres are carefully arranged such that up to 10 polarization states of the single emitter, including linear, circular, and elliptical polarizations, can be distinguished via the distinct field localization in four gaps. The ability to transform polarization states into field spatial localizations may find application in single emitter polarization analysis.     

Quantitative nanoorganized structural evolution for a high efficiency bulk heterojunction polymer solar cell

We have developed an improved small-angle X-ray scattering (SAXS) model and analysis methodology to quantitatively evaluate the nanostructures of a blend system. This method has been applied to resolve the various structures of self-organized poly(3-hexylthiophene)/C61-butyric acid methyl ester (P3HT/PCBM) thin active layer in a solar cell from the studies of both grazing-incidence small-angle X-ray scattering (GISAXS) and grazing-incidence X-ray diffraction (GIXRD). Tuning the various length scales of PCBM-related structures by a different annealing process can provide a flexible approach and better understanding to enhance the power conversion of the P3HT/PCBM solar cell. The quantitative structural characterization by this method includes (1) the mean size, volume fraction, and size distribution of aggregated PCBM clusters, (2) the specific interface area between PCBM and P3HT, (3) the local cluster agglomeration, and (4) the correlation length of the PCBM molecular network within the P3HT phase. The above terms are correlated well with the device performance. The various structural evolutions and transformations (growth and dissolution) between PCBM and P3HT with the variation of annealing history are demonstrated here. This work established a useful SAXS approach to present insight into the modeling of the morphology of P3HT/PCBM film. In situ GISAXS measurements were also conducted to provide informative details of thermal behavior and temporal evolution of PCBM-related structures during phase separation. The results of this investigation significantly extend the current knowledge of the relationship of bulk heterojunction morphology to device performance.     

Effects of molecular architectures and solvophobic additives on the aggregative properties of polymeric surfactants

The aggregative behavior of the polymeric surfactants with various molecular architectures in dilute solutions is studied by dissipative particle dynamics. The effects of the solvophobic/solvophilic length, polymeric architecture (linear, star, dendritic, and cyclic type), chain rigidity, and solvophobic additives on the critical micelle concentration (CMC) and the aggregative patterns are systematically investigated. It is found that molecular architectures have a noteworthy impact on the aggregative properties. For linear diblock copolymers, the CMC declines with increasing solvophobic length but rises with increasing solvophilic length. Nonetheless, the solvophobic group has comparatively greater influence on the CMC. Imposition of the star, dendritic, or cyclic structures onto the solvophobic or solvophilic parts of the polymeric surfactant leads to an increase in the CMC. On the contrary, polymers imposed with the greater degree of the rigidity on the solvophobic or solvophilic block have lower CMC. The addition of solvophobic additives results in a decrease of CMC as well. The effects of the concentration and length of the additives on the aggregative behaviors of polymer surfactants were investigated. Interesting supramolecular structures such as caterpillar and worm-like micelles were observed.     

Effect of hydroxypropyl-β-cyclodextrin complexation on the aqueous solubility, structure, thermal stability, antioxidant activity, and tyrosinase inhibition of paeonol

The objective of this paper is to study the effect of hydroxypropyl-β-cyclodextrin (HP-β-CD) complexation on the aqueous solubility, structure, thermal stability, antioxidant activity, and tyrosinase inhibition of paeonol (PAE). The inclusion complex (PAE-HP-β-CD complex) of HP-β-CD and PAE was prepared by a freeze-drying method. Phase solubility tests showed that the stability constant of the inclusion complex was about 33.8?M^?1 at 25?°C. The experimental results of proton nuclear magnetic resonance (H-NMR) spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) suggested that PAE was included by HP-β-CD to form the PAE-HP-β-CD complex. Furthermore, the thermogravimetric analysis (TGA) results showed that the thermal stability of PAE was improved when it was complexed with HP-β-CD. Comparing the antioxidant activity of PAE with that of the PAE-HP-β-CD complex at the same concentration revealed that the complex of PAE with HP-β-CD was better able to eliminate radical. Furthermore, the experimental results revealed that the formation of a complex with HP-β-CD increased the water solubility of PAE, improving its apparent inhibitive activity of tyrosinase.     

Size-dependent properties of small unilamellar vesicles formed by model lipids

The size-dependent behavior of small unilamellar vesicles is explored by dissipative particle dynamics, including the membrane characteristics and mechanical properties. The spontaneously formed vesicles are in the metastable state and the vesicle size is controlled by the concentration of model lipids. As the vesicle size decreases, the bilayer gets thinner and the area density of heads declines. Nonetheless, the area density in the inner leaflet is higher than that in the outer. The packing parameters are calculated for both leaflets. The result indicates that the shape of lipid in the outer leaflet is like a truncated cone but that in the inner leaflet resembles an inverted truncated cone. Based on a local order parameter, our simulations indication that the orientation order of lipid molecules decreases as the size of the vesicle reduces and this fact reveals that the bilayer becoming thinner for smaller vesicle is mainly attributed to the orientation disorder of the lipids. The membrane tension can be obtained through the Young-Laplace equation. The tension is found to grow with reducing vesicle size. Therefore, small vesicles are less stable against fusion. Using the inflation method, the area stretching and bending moduli can be determined and those moduli are found to grow with reducing size. Nonetheless, a general equation with a single numerical constant can relate bending modulus, area stretching modulus, and bilayer thickness irrespective of the vesicle size. Finally, a simple metastable model is proposed to explain the size-dependent behavior of bilayer thickness, orientation, and tension.     

BPM Simulation and Comparison of 1 × 2 Directional Waveguide Coupling and Y-Junction Coupling Silicon-on-Insulator Optical Couplers

For developing large area opto-electronic silicon-on-insulator (SOI) devices, the optical coupler is a basic key device. In this article, the authors design and simulate 1 2 2 directional waveguide coupling and Y-branch coupling optical couplers based on Unibond SOI rib waveguides. The beam propagation method (BPM) is used for light propagation analysis. The simulation results and comparisons of the two kinds of optical couplers are reported. The S-bend waveguide for attaching to the two kinds of SOI optical coupler is also analyzed by BPM. We find that the directional coupler has lower power loss, but the Y-junction coupler is more wavelength insensitive with the same device size and splitting angle. The fabrication tolerance analysis shows Y-junction coupler has better fabrication characteristics.     

Donnan potential of dilute colloidal dispersions: Monte Carlo simulations

Donnan equilibrium between a salt-free colloidal dispersion and an electrolyte solution has been investigated by Monte Carlo simulations. The Donnan potential is directly calculated by considering two compartments separated by a semipermeable membrane. In order to understand the role played by colloid–ion interactions, the influences of colloidal characteristics, including particle size R, intrinsic particle charge Z, counterion valency z_c, and concentration c_p, on Donnan potential Ψ_D and effective charge Z_eff are examined. Our simulations show that the electroneutrality condition is not followed in both compartments and the Donnan potential arises due to the net charge density. The Donnan potential grows by increasing c_p and Z_eff and by decreasing dielectric constant ε_r, i.e., Ψ_DZ_effc_p/ε_r approximately. Note that the effective charge varies with R,Z,c_p,ε_r and z_c as well. When the salt concentration is increased, the net charge density is lowered and thus the Donnan potential decays accordingly. The validity of the classical theory based on the Nernst equation and the electroneutrality assumption is also examined. In general, the simulation results at high-salt condition can be well represented by such mean-field theory.     

Structure-based design of carboxybiphenylindole inhibitors of the ZipA-FtsZ interaction

Structural features of two weak inhibitors of the ZipA-FtsZ protein-protein interaction which were found to bind to overlapping but different areas of the key binding site were combined in one new series of carboxybiphenyl-indoles with improved inhibitory activity.     

Tetraethanolammonium counterions in surfactant and classical colloidal systems

Interaction forces between mica surfaces as a function of added tetraethanolammonium bromide, (EtOH)₄NBr, were determined using surface forces measurements. Critical micelle concentrations and aggregation numbers were determined for tetraethanolammonium dodecylsulfate, (EtOH)₄NDS, using surface tension and fluorescence probe-quencher measurements. The properties of the large hydrophilic counterion (EtOH)₄N⁺ are compared to those of its hydrophobic analogue Pr₄N⁺.     

A Green BODIPY‐Based,Super‐Fluorogenic,Protein‐Specific Labelling Agent

We report the development of YC23, a novel green BODIPY‐based dimaleimide derivative that undergoes a fluorogenic addition reaction (FlARe) with a genetically encodable peptide tag (dC10α) that can be fused to a protein of interest (POI). We also demonstrate the application of this reaction for the fluorogenic labelling of a specific POI in bacterial lysate and in living mammalian cells.